Systems and methods for spinal fusion

ABSTRACT

A system and method for spinal fusion comprising a spinal fusion implant of non-bone construction releasably coupled to an insertion instrument dimensioned to introduce the spinal fusion implant into any of a variety of spinal target sites.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is continuation of U.S. patent application Ser. No.13/441,092 filed Apr. 6, 2012, which is continuation of U.S. patentapplication Ser. No. 13/440,062 filed Apr. 5, 2012 (now U.S. Pat. No.8,246,686), which is a continuation of U.S. patent application Ser. No.13/079,645 filed Apr. 4, 2011 (now U.S. Pat. No. 8,187,334), which iscontinuation of U.S. patent application Ser. No. 11/093,409 filed Mar.29, 2005 (now U.S. Pat. No. 7,918,891), which claims the benefit of thefiling date under 35 USC 119(e) of United States Provisional Applicationentitled “Systems and Methods for Spinal Fusion,” Ser. No. 60/557,536filed Mar. 29, 2004, the entire contents of these prior applications areincorporated herein by reference.

BACKGROUND OF THE INVENTION

I. Field of the Invention

The present invention relates generally to spinal surgery and, moreparticularly, to a system and method for spinal fusion comprising aspinal fusion implant of non-bone construction releasably coupled to aninsertion instrument dimensioned to introduce the spinal fusion implantinto any of a variety of spinal target sites.

II. Discussion of the Prior Art

Currently there are nearly 500,000 spine lumbar and cervical fusionprocedures performed each year in the United States. Such procedures arecommonly performed to correct problems, such as chronic back or neckpain, which result from degenerated intervertebral discs or trauma.Generally, spinal fusion procedures involve removing some or all of thediseased or damaged disc, and inserting one or more intervertebralimplants into the resulting disc space. Introducing the intervertebralimplant serves to restore the height between adjacent vertebrae (“discheight”), which reduces if not eliminates neural impingement commonlyassociated with a damaged or diseased disc.

Autologous bone grafts are widely used intervertebral implant for lumbarfusion. Autologous bone grafts are obtained by harvesting a section ofbone from the iliac crest of the patient and thereafter implanting thearticle of autologous bone graft to effect fusion. While generallyeffective, the use of autologous bone grafts suffers certain drawbacks.A primary drawback is the morbidity associated with harvesting theautologous graft from the patient's iliac crest. Another relateddrawback is the added surgical time required to perform thebone-harvesting.

Allograft bone grafts have been employed with increased regularity in aneffort to overcome the drawbacks of autologous bone grafts. Allograftbone grafts are harvested from cadaveric specimens, machined, andsterilized for implantation. While allograft bone grafts eliminate themorbidity associated with iliac crest bone harvesting, as well asdecrease the overall surgical time, they still suffer certain drawbacks.A primary drawback is supply constraint, in that the tissue banks thatprocess and produce allograft bone implants find it difficult toforecast allograft given the inherent challenges in forecasting thereceipt of cadavers. Another related drawback is that it is difficult tomanufacture the allograft with consistent shape and strengthcharacteristics given the variation from cadaver to cadaver.

The present invention is directed at overcoming, or at least improvingupon, the disadvantages of the prior art.

SUMMARY OF THE INVENTION

The present invention overcomes the drawbacks of the prior art byproviding a spinal fusion system and related methods involving the useof a spinal fusion implant of non-bone construction. The non-boneconstruction of the spinal fusion implant of the present inventionovercomes the drawbacks of the prior art in that it is not supplylimited (as with allograft) and does not require harvesting bone fromthe patient (as with autograft). The spinal fusion implant of thepresent invention may be comprised of any suitable non-bone composition,including but not limited to polymer compositions (e.g.poly-ether-ether-ketone (PEEK) and/or poly-ether-ketone-ketone (PEKK)),ceramic, metal or any combination of these materials.

The spinal fusion implant of the present invention may be provided inany number of suitable shapes and sizes depending upon the particularsurgical procedure or need. The spinal fusion implant of the presentinvention may be dimensioned for use in the cervical and/or lumbar spinewithout departing from the scope of the present invention. For lumbarfusion, the spinal fusion implant of the present invention may bedimensioned, by way of example only, having a width ranging between 9and 18 mm, a height ranging between 8 and 16 mm, and a length rangingbetween 25 and 45 mm. For cervical fusion, the spinal fusion implant ofthe present invention may be dimensioned, by way of example only, havinga width about 11 mm, a height ranging between 5 and 12 mm, and a lengthabout 14 mm.

The spinal fusion implant of the present invention may be provided withany number of additional features for promoting fusion, such asapertures extending between the upper and lower vertebral bodies whichallow a boney bridge to form through the spinal fusion implant of thepresent invention. Such fusion-promoting apertures may be dimensioned toreceive any number of suitable osteoinductive agents, including but notlimited to bone morphogenic protein (BMP) and bio-resorbable polymers,including but not limited to any of a variety of poly(D,L-lactide-co-glycolide) based polymers. The spinal fusion implant ofthe present invention is preferably equipped with one or more lateralopenings which aid it provides in visualization at the time ofimplantation and at subsequent clinical evaluations.

The spinal fusion implant of the present invention may be provided withany number of suitable anti-migration features to prevent spinal fusionimplant from migrating or moving from the disc space after implantation.Suitable anti-migration features may include, but are not necessarilylimited to, angled teeth formed along the upper and/or lower surfaces ofthe spinal fusion implant and/or spike elements disposed partiallywithin and partially outside the upper and/or lower surfaces of thespinal fusion implant. Such anti-migration features provide theadditional benefit of increasing the overall surface area between thespinal fusion implant of the present invention and the adjacentvertebrae, which promotes overall bone fusion rates.

The spinal fusion implant of the present invention may be provided withany number of features for enhancing the visualization of the implantduring and/or after implantation into a spinal target site. According toone aspect of the present invention, such visualization enhancementfeatures may take the form of the spike elements used foranti-migration, which may be manufactured from any of a variety ofsuitable materials, including but not limited to a metal, ceramic,and/or polymer material, preferably having radiopaque characteristics.The spike elements may also take any of a variety of suitable shapes,including but not limited to a generally elongated element disposedwithin the implant such that the ends thereof extend generallyperpendicularly from the upper and/or lower surfaces of the implant. Thespike elements may each comprise a unitary element extending throughupper and lower surfaces or, alternatively, each spike element maycomprise a shorter element which only extends through a single surface(that is, does not extend through the entire height of the implant). Inany event, when the spike elements are provided having radiodensecharacteristics and the implant is manufactured from a radiolucentmaterial (such as, by way of example only, PEEK and/or PEKK), the spikeelements will be readily observable under X-ray or fluoroscopy such thata surgeon may track the progress of the implant during implantationand/or the placement of the implant after implantation.

The spinal implant of the present invention may be introduced into aspinal target site through the use of any of a variety of suitableinstruments having the capability to releasably engage the spinalimplant. In a preferred embodiment, the insertion instrument permitsquick, direct, accurate placement of the spinal implant of the presentinvention into the intervertebral space. According to one embodiment,the insertion instrument includes a threaded engagement elementdimensioned to threadably engage into a receiving aperture formed in thespinal fusion implant of the present invention. According to anotherembodiment, the insertion instrument includes an elongate fork memberand a generally tubular lock member.

BRIEF DESCRIPTION OF THE DRAWINGS

Many advantages of the present invention will be apparent to thoseskilled in the art with a reading of this specification in conjunctionwith the attached drawings, wherein like reference numerals are appliedto like elements and wherein:

FIG. 1 is a perspective view of a spinal fusion system of the presentinvention, including a lumbar fusion implant releasably coupled to aninsertion instrument according to one embodiment of the presentinvention;

FIG. 2 is a perspective view of the lumbar fusion implant of FIG. 1,illustrating (among other things) fusion apertures extending between topand bottom surfaces, a plurality of visualization apertures extendingthrough the side walls, and a variety of anti-migration featuresaccording to one embodiment of the present invention;

FIG. 3 is a top view of the lumbar fusion implant of FIG. 1,illustrating (among other things) the fusion apertures and theanti-migration features according to one embodiment of the presentinvention;

FIG. 4 is a side view of the lumbar fusion implant of FIG. 1,illustrating (among other things) the visualization apertures, theanti-migration feature, and a receiving aperture for releasably engagingthe insertion instrument of FIG. 1 according to one embodiment of thepresent invention;

FIG. 5 is an end view of the lumbar fusion implant of FIG. 1,illustrating (among other things) the receiving aperture formed in theproximal end, the anti-migration features, and the visualizationapertures according to one embodiment of the present invention;

FIG. 6 is an enlarged side view of the lumbar fusion implant of FIG. 1releasably coupled to the distal end of the insertion instrument of FIG.1 according to one embodiment of the present invention;

FIG. 7 is a perspective view of the insertion instrument of FIG. 1 in afully assembled form according to one embodiment of the presentinvention;

FIG. 8 is an enlarged perspective view of the distal region of theinsertion instrument of FIG. 1 according to one embodiment of thepresent invention;

FIG. 9 is a perspective exploded view of the insertion instrument ofFIG. 1, illustrating the component parts of the insertion instrumentaccording to one embodiment of the present invention;

FIG. 10 is a perspective view of a spinal fusion system of the presentinvention, including a cervical fusion implant releasably coupled to acervical insertion instrument according to one embodiment of the presentinvention;

FIG. 11 is a perspective view of the proximal side of the cervicalfusion implant of FIG. 10, illustrating (among other things) fusionapertures extending between top and bottom surfaces, a plurality ofvisualization apertures extending through the lateral walls, a pluralityof receiving apertures, and a variety of anti-migration featuresaccording to one embodiment of the present invention;

FIG. 12 is a perspective view of the distal side cervical fusion implantof FIG. 10, illustrating (among other things) the visualizationapertures and anti-migration features;

FIG. 13 is a top view of the cervical fusion implant of FIG. 10,illustrating (among other things) the fusion apertures andanti-migration features according to one embodiment of the presentinvention;

FIG. 14 is a side view of the cervical fusion implant of FIG. 10,illustrating (among other things) the visualization apertures, theanti-migration features, and one of two receiving apertures provided inthe proximal end for releasably engaging the cervical insertioninstrument of FIG. 10 according to one embodiment of the presentinvention;

FIG. 15 is a perspective view of the cervical fusion implant of thepresent invention just prior to attachment to the cervical insertiondevice according to one embodiment of the present invention;

FIG. 16 is a perspective view of the insertion instrument of FIG. 10 ina fully assembled form according to one embodiment of the presentinvention;

FIG. 17 is a perspective exploded view of the insertion instrument ofFIG. 10, illustrating the component parts of the insertion instrumentaccording to one embodiment of the present invention;

FIGS. 18 and 19 are perspective and side views, respectively,illustrating the “enhanced visualization” feature of the presentinvention as employed within a lumbar fusion implant according to oneembodiment of the present invention;

FIGS. 20 and 21 are perspective and side views, respectively,illustrating the “enhanced visualization” feature of the presentinvention as employed within a lumbar fusion implant according to oneembodiment of the present invention; and

FIGS. 22 and 23 are perspective and side views, respectively,illustrating the “enhanced visualization” feature of the presentinvention as employed within a cervical fusion implant according to oneembodiment of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Illustrative embodiments of the invention are described below. In theinterest of clarity, not all features of an actual implementation aredescribed in this specification. It will of course be appreciated thatin the development of any such actual embodiment, numerousimplementation-specific decisions must be made to achieve thedevelopers' specific goals, such as compliance with system-related andbusiness-related constraints, which will vary from one implementation toanother. Moreover, it will be appreciated that such a development effortmight be complex and time-consuming, but would nevertheless be a routineundertaking for those of ordinary skill in the art having the benefit ofthis disclosure. The system to facilitate bone fusion and relatedmethods disclosed herein boasts a variety of inventive features andcomponents that warrant patent protection, both individually and incombination.

FIG. 1 illustrates, by way of example only, a spinal fusion system 5 forperforming spinal fusion between adjacent lumbar vertebrae, including anexemplary spinal fusion implant 10 and an exemplary insertion instrument20 provided in accordance with the present invention. The spinal fusionimplant 10 may be comprised of any suitable non-bone composition havingsuitable radiolucent characteristics, including but not limited topolymer compositions (e.g. poly-ether-ether-ketone (PEEK) and/orpoly-ether-ketone-ketone (PEKK)) or any combination of PEEK and PEKK.The spinal fusion implant 10 of the present invention may bedimensioned, by way of example only, having a width ranging between 9and 18 mm, a height ranging between 8 and 16 mm, and a length rangingbetween 25 and 45 mm.

As will be described in detail below, the insertion instrument 20 isconfigured to releasably maintain the exemplary spinal fusion implant 10in the proper orientation during insertion into a lumbar disc space andthereafter release to deposit the implant 10. The exemplary spinalfusion implant 10, having been deposited in the disc space, facilitatesspinal fusion over time by maintaining a restored disc height as naturalbone growth occurs through and/or past the implant 10, resulting in theformation of a boney bridge extending between the adjacent vertebralbodies. The implant 10 is particularly suited for introduction into thedisc space via a lateral (trans-psoas) approach to the spine, but may beintroduced in any of a variety of approaches, such as posterior,anterior, antero-lateral, and postero-lateral, without departing fromthe scope of the present invention (depending upon the sizing of theimplant 10).

The spinal fusion implant 10 of the present invention may be providedwith any number of additional features for promoting fusion, such asapertures 2 extending between the upper and lower vertebral bodies whichallow a boney bridge to form through the spinal fusion implant 10.According to a still further aspect of the present invention, thisfusion may be facilitated or augmented by introducing or positioningvarious osteoinductive materials within the apertures 2 and/or adjacentto the spinal fusion implant 10. Such osteoinductive materials may beintroduced before, during, or after the insertion of the exemplaryspinal fusion implant 10, and may include (but are not necessarilylimited to) autologous bone harvested from the patient receiving thespinal fusion implant 10, bone allograft, bone xenograft, any number ofnon-bone implants (e.g. ceramic, metallic, polymer), bone morphogenicprotein, and bio-resorbable compositions, including but not limited toany of a variety of poly (D,L-lactide-co-glycolide) based polymers.

The spinal fusion implant 10 of the present invention is preferablyequipped with one or more visualization apertures 4 situated along thelateral sides, which aid in visualization at the time of implantationand at subsequent clinical evaluations. More specifically, based on thegenerally radiolucent nature of the implant 10, the visualizationapertures 4 provide the ability to visualize the interior of the implant10 during X-ray and/or other suitable imaging techniques which areundertaken from the side (or “lateral”) perspective of the implant 10.If fusion has taken place, the visualization apertures 4 will provide amethod for the surgeon to make follow up assessments as to the degree offusion without any visual interference from the spinal fusion implant10. Further, the visualization apertures 4 will provide an avenue forcellular migration to the exterior of the spinal fusion implant 10. Thusthe spinal fusion implant 10 will serve as additional scaffolding forbone fusion on the exterior of the spinal fusion implant 10.

FIGS. 2-5 depict various embodiments of the exemplary spinal fusionimplant 10. Some common attributes are shared among the variousembodiments. More specifically, each spinal fusion implant 10 has a topsurface 31, a bottom surface 33, lateral sides 14, a proximal side 22,and a distal side 16. In one embodiment, the top and bottom surfaces 31,33 are generally parallel. It can be appreciated by one skilled in theart that although the surfaces 31, 33 are generally parallel to oneanother, they may be provided in any number of suitable shapes,including but not limited to concave and/or convex. When provided asconvex shapes, the top and bottom surfaces 31, 33 may better match thenatural contours of the vertebral end plates. Although not shown, itwill be appreciated that the top and bottom surfaces 31, 33 may beangled relative to one another to better match the natural lordosis ofthe lumbar and cervical spine or the natural kyphosis of the thoracicspine.

The exemplary spinal fusion implant 10 also preferably includesanti-migration features designed to increase the friction between thespinal fusion implant 10 and the adjacent contacting surfaces of thevertebral bodies so as to prohibit migration of the spinal fusionimplant 10 after implantation. Such anti-migration features may includeridges 6 provided along the top surface 31 and/or bottom surface 33.Additional anti-migration features may also include a pair of spikeelements 7 disposed within the proximal region of the implant 10, a pairof spike elements 8 disposed within the distal region of the implant 10,and a pair of spike elements 9 disposed within the central region of theimplant 10. Spike elements 7, 8, 9 may extend from the top surface 31and/or bottom surface 33 within the respective proximal, distal andcentral regions of the implant 10. The spike elements 7, 8, 9 may bemanufactured from any of a variety of suitable materials, including butnot limited to a metal, ceramic, and/or polymer material, preferablyhaving radiopaque characteristics. The spike elements 7, 8, 9 may alsotake any of a variety of suitable shapes, including but not limited to agenerally elongated element disposed within the implant 10 such that theends thereof extend generally perpendicularly from the upper and/orlower surfaces 31, 33 of the implant 10. As best appreciated in FIG. 4,the spike elements 7, 8, 9 may each comprise a unitary element extendingthrough upper and lower surfaces 31, 33. Alternatively, each spikeelement 7, 8, 9 may comprise a shorter element which only extendsthrough a single surface 31, 33 (that is, does not extend through theentire height of the implant 10). In any event, when the spike elements7, 8, 9 are provided having radiodense characteristics and the implant10 is manufactured from a radiolucent material (such as, by way ofexample only, PEEK and/or PEKK), the spike elements 7, 8, 9 will bereadily observable under X-ray or fluoroscopy such that a surgeon maytrack the progress of the implant 10 during implantation and/or theplacement of the implant 10 after implantation.

The spinal fusion implant 10 has two large fusion apertures 2, separatedby a medial support 50, extending in a vertical fashion through the topsurface 31 and bottom surface 33. The fusion apertures 2 functionprimarily as an avenue for bony fusion between adjacent vertebrae. Thefusion apertures 2 may be provided in any of a variety of suitableshapes, including but not limited to the generally rectangular shapebest viewed in FIG. 3, or a generally circular, oblong and/or triangularshape or any combination thereof. The spinal fusion implant 10 may havea plurality of visualization apertures 4 which allow a clinician to makevisual observations of the degree of bony fusion un-obscured by thelateral side 14 to facilitate further diagnosis and treatment. Thevisualization apertures 4 may be provided in any of a variety ofsuitable shapes, including but not limited to the generally oblong shapebest viewed in FIG. 4, or a generally circular, rectangular and/ortriangular shape or any combination thereof.

The spinal fusion implant 10 may be provided with any number of suitablefeatures for engaging the insertion instrument 20 without departing fromthe scope of the present invention. As best viewed in FIGS. 4-6, oneengagement mechanism involves providing a threaded receiving aperture 12in the proximal sidewall 22 of the spinal fusion implant 10 of thepresent invention. The threaded receiving aperture 12 is dimensioned tothreadably receive a threaded connector 24 on the insertion instrument20 (as will be described in greater detail below). The receivingaperture 12 extends inwardly from the proximal side 22 in a generallyperpendicular fashion relative to the proximal side 22. Although shownas having a generally circular cross-section, it will be appreciatedthat the receiving aperture 12 may be provided having any number ofsuitable shapes or cross-sections, including but not limited torectangular or triangular. In addition to the receiving aperture 12, thespinal fusion implant 10 is preferably equipped with a pair of groovedpurchase regions 60, 61 extending generally horizontally from eitherside of the receiving aperture 12. The grooved purchase regions 60, 61are dimensioned to receive corresponding distal head ridges 62, 63 onthe insertion instrument 20 (as will be described in greater detailbelow), which collectively provide an enhanced engagement between theimplant 10 and instrument 20.

FIGS. 6-9 detail the exemplary insertion instrument 20 according to oneembodiment of the invention. The exemplary insertion instrument 20includes an elongate tubular element 28 and an inserter shaft 44. Theelongate tubular element 28 is constructed with a distal head 26 at itsdistal end, distal head ridges 62, 63 on the distal end of the distalhead 26, a thumbwheel housing 38 at its proximal end and a handle 42 atits proximal end. The elongate tubular element 28 is generallycylindrical and of a length sufficient to allow the device to span fromthe surgical target site to a location sufficiently outside thepatient's body so the handle 42 and thumbwheel housing 38 can be easilyaccessed by a clinician or a complimentary controlling device.

The elongate tubular element 28 is dimensioned to receive a spring 46and the proximal end of the inserter shaft 44 into the inner bore 64 ofthe elongate tubular element 28. The inserter shaft 44 is dimensionedsuch that the threaded connector 24 at the distal end of the insertershaft 44 just protrudes past the distal head ridges 62, 63 to allowengagement with the receiving aperture 12 of the spinal fusion implant10. It should be appreciated by one skilled in the art that such aconstruction allows the inserter shaft 44 to be able to rotate freelywithin the elongate tubular element 28 while stabilized by a spring 46to reduce any slidable play in the insertion instrument 20.

The handle 42 is generally disposed at the proximal end of the insertioninstrument 20. The handle 42 is fixed to the thumbwheel housing 38allowing easy handling by the clinician. Because the handle 42 is fixedthe clinician has easy access to the thumbwheel 34 and can stably turnthe thumbwheel 34 relative to the thumbwheel housing 38. Additionally,the relative orientation of the thumbwheel housing 38 to the handle 42orients the clinician with respect to the distal head 26 and distal headridge 62. By way of example, the thumbwheel housing 38 holds athumbwheel 34, a set screw 32, and a spacer 36. The inserter shaft 44 isattached to the thumbwheel 34 and is freely rotatable with low frictiondue to the spacer 36. One skilled in the art can appreciate myriadmethods of assembling a housing similar to the above described.

FIG. 6 details the distal head ridge of the exemplary insertioninstrument 20 coupled to the spinal fusion implant 10 through thepurchase regions 60, 61. The distal head ridges 62, 63 are dimensionedto fit slidably into the purchase regions 60, 61 with low friction toallow accurate engagement of the threaded connector 24 to the receivingaperture 12 of the spinal fusion implant 10. In the presentedembodiment, the outer dimension of the threaded connector 24 is smallerthan the largest outer dimension of the distal head 26 and elongatetubular element 28. Alternatively, other methods of creating a grippingsurface are contemplated including but not limited to knurling orfacets.

In order to use the system to perform a spinal fusion procedure, theclinician must first designate the appropriate implant size. After thespinal fusion implant 10 is chosen, the distal head ridges 62, 63 of theinserter shaft 44 are inserted into the purchase regions 60, 61 of thespinal fusion implant 10. At that time the spinal fusion implant 10 andinsertion instrument 20 are slidably engaged with one another. Beforethe clinician can manipulate the combined spinal fusion implant 10 andinsertion instrument 20, they must be releasably secured together. Inorder to secure the spinal fusion implant 10 onto the threaded connector24 of the inserter instrument 20, the clinician employs the thumbwheel34 to rotate the inserter shaft 44 and threaded connector 24. Therotation of the threaded connector 24 will releasably engage thereceiving aperture of the spinal fusion implant 10 and stabilize theinsertion instrument 20 relative to the spinal fusion implant 10.

A clinician can utilize the secured system in either an open orminimally invasive spinal fusion procedure. In either type of procedure,a working channel is created in a patient that reaches the targetedspinal level. After the creation of that channel, the intervertebralspace may be prepared via any number of well known preparation tools,including but not limited to kerrisons, rongeurs, pituitaries, andrasps. After preparation, the insertion instrument 20 is used to place aspinal fusion implant 10 into the prepared intervertebral space. Oncethe implant 10 is inserted into the prepared space, the implant 10 isreleased from the insertion instrument 20 by rotating the thumbwheel 34to disengage the threaded connector 24 from the receiving aperture 12.That motion removes the compressive force on the purchase regions 60, 61between the distal head 26 and the distal head ridges 62, 63 of thespinal fusion implant 10 and allows the insertion instrument to beslidably removed from the implant 10. After the threaded connector 24 isdisengaged from the implant 10, the insertion instrument 20 is removedfrom the working channel and the channel is closed. As previouslymentioned, additional materials may be included in the procedure before,during or after the insertion of the spinal fusion implant 10 to aid thenatural fusion of the targeted spinal level.

FIG. 10 illustrates a spinal fusion system 105 for performing spinalfusion between adjacent cervical vertebrae, including an exemplaryspinal fusion implant 110 and an exemplary cervical insertion instrument120 provided in accordance with the present invention. The spinal fusionimplant 110 may comprise of any suitable non-bone composition havingsuitable radiolucent characteristics, including but not limited topolymer compositions (e.g. poly-ether-ether-ketone (PEEK) and/orpoly-ether-ketone-ketone (PEKK)) or any combination of PEEK and PEKK.The spinal fusion implant 110 may be provided in any number of suitablesizes, such as, by way of example only, a width ranging between 11 to 14mm, a height ranging between 5 and 12 mm, and a length ranging from 14and 16 mm.

As will be described in detail below, the cervical insertion instrument120 is configured to releasably maintain the exemplary cervical fusionimplant 110 in the proper orientation for insertion. The cervical fusionimplant 110 may be simultaneously introduced into a disc space whilelocked within the cervical insertion instrument 120 and thereafterreleased. The exemplary cervical fusion implant 110, having beendeposited in the disc space, effects spinal fusion over time as thenatural bone healing process integrates and binds the implant with theadjacent vertebral bodies. This fusion may be facilitated or augmentedby introducing or positioning various materials in a space createdwithin or adjacent to the cervical fusion implant 110. Those materialsmay be introduced before, during, or after the insertion of theexemplary cervical fusion implant 110. The additional material mayinclude bone autograft harvested from the patient receiving the spinalfusion implant 10, one or more additional bone allograft,bio-resorbables or xenograft implants, any number of non-bone implants,and any number of fusion promoting compounds such as bone morphogenicprotein.

FIGS. 11-14 depict various embodiments of the exemplary cervical fusionimplant 110. Some common attributes are shared among the variousembodiments. More specifically, each cervical fusion implant 110 has atop surface 31, a bottom surface 33, lateral sides 14, a proximal side22, and a distal side 16. In one embodiment, the top and bottom surfaces31, 33 are generally parallel. It can be appreciated by one skilled inthe art that although the surfaces are generally parallel, that the top31 and bottom 33 surfaces may be angled with respect to one another tomatch the natural curve of the spine (i.e. lordosis or kyphosis). By wayof example, implants for the cervical or lumbar regions of the spinewill have anterior height greater than the posterior height to match thenatural lordosis in those regions. Inversely, the implants designed forimplantation into the thoracic region will be manufactured with aposterior height greater than the anterior height to match the naturalkyophosis in that region. Additionally, the angled surface can aid inoverall fit within the vertebral disc space.

The cervical fusion implant 110 preferably includes two receivingapertures 12 which are centrally aligned on the proximal side 22. Thereceiving apertures 12 extend inwardly from the proximal side 22 in agenerally perpendicular fashion relative to the proximal side 22.Although shown as having a generally circular cross-section, it will beappreciated that the receiving aperture 12 may be provided having anynumber of suitable shapes or cross-sections, including but not limitedto rectangular or triangular.

The exemplary cervical fusion implant 110 also preferably includesanti-migration features such as anti-migration teeth 6 along the topsurface 31 and bottom surface 33. Additional anti-migration features mayinclude a plurality of proximal anti-migration spikes 68 and/or distalanti-migration spikes 70 integrated vertically through the cervicalfusion implant 110. The anti-migration features increase the frictionbetween the cervical fusion implant 110 and the adjacent contactingsurfaces of the vertebral bodies. That friction prohibits migration ofthe cervical fusion implant 110 during the propagation of natural bonyfusion. It should be appreciated by one skilled in the art that suchanti-migration teeth 6 can be oriented in a any manner other thangenerally vertically (as shown) without departing from the scope of thepresent invention. Moreover, as described above, the spikes 68, 70 maybe constructed from any of a variety of radiopaque materials, includingbut not limited to a metal, ceramic, and/or polymer material. When thespike elements 68, 70 are provided having such radiodensecharacteristics, and the implant 110 is manufactured from a radiolucentmaterial (such as, by way of example only, PEEK and/or PEKK), the spikeelements 68, 70 will be readily observable under X-ray or fluoroscopysuch that a surgeon may track the progress of the implant 110 duringimplantation and/or the placement of the implant 110 after implantation.

The cervical fusion implant 110 has one large fusion aperture 2,extending in a vertical fashion through the top surface 31 and bottomsurface 33 which will function primarily as the avenue for bony fusionbetween adjacent vertebrae. The cervical fusion implant 110 may have aplurality of visualization apertures 4 which can also serve as an avenueof bony fusion on the lateral sides 14 via cell migration or additionaladjuvants. The visualization apertures 4 serve an additional function ofallowing a clinician to make visual observations of the degree of bonyfusion un-obscured by the lateral side 14 to facilitate furtherdiagnosis and treatment.

FIG. 15 illustrates, by way of example, the orientation of the cervicalfusion implant 110 prior to attachment to the cervical insertioninstrument 120 by a clinician. One skilled in the art would appreciatethat although the current embodiment shows a slidable engagement,various other methods of engagement are contemplated, such as,threadable or hooking features.

FIGS. 16-17 detail the tubular lock member 21 of the exemplary cervicalinserter instrument 110. The tubular lock member 21 includes a centralbore 25 dimensioned to receive the proximal end of the elongate forkmember 11 therein. The internal dimension of the central bore 25 issmaller than the largest freestanding outer dimension of the taperfeature 19. As a result, the portion of the elongate fork member 11 thatmay be received by the central bore 25 of the tubular lock member 21 islimited by interference between the distal end of the tubular lockmember 21 and the taper feature 19 of the elongate fork member 11. Inthe present embodiment, the outer dimension of the threaded feature 13of the elongate fork member 11 is smaller than the largest outerdimension of the taper feature 19 on the elongate fork member 11. Athread feature 23 (not shown) at the proximal end of the tubular lockmember 21 is situated inside the central bore 25. The thread feature 23matches the thread feature 13 on the elongate fork member 11 so thatthey can be threadably attached to one another. To ease the rotation ofthe tubular lock member 21 by hand, two semi-circular wings 27 may beprovided protruding laterally outward from either side of the tubularlock member 21. Alternatively, other methods of creating a grippingsurface are contemplated including but not limited to knurling orfacets.

A clinician can utilize the secured system in either an open orminimally invasive spinal fusion procedure. In either type of procedure,a working channel is created in a patient that reaches the targetedspinal level. After the creation of that channel, the intervertebralspace would be prepared (via known instruments as described above).After preparation, the insertion instrument 120 is used to place acervical fusion implant 110 into the prepared intervertebral space. Oncethe cervical fusion implant 110 is inserted into the prepared space, theimplant 110 is released from the cervical insertion instrument 120 byretracting the tubular lock member 21 from the elongate fork member 11by rotating the tubular lock member 21 with respect to the elongate forkmember 11 in the opposite direction from that used to initially securethe implant 110. That motion removes the compressive force on thepurchase region 39 between the apertures 12 of the cervical fusionimplant 110 and allows the engagement features 17 to be slidably removedfrom the apertures 12. After the engagement features 17 are disengagedfrom the cervical fusion implant 110, the cervical inserter instrument120 is removed from the working channel and the channel is closed. Aspreviously mentioned, additional materials may be included in theprocedure before, during or after the insertion of the cervical fusionimplant 110 to aid the natural fusion of the targeted spinal level.

In order to use the system to perform a spinal fusion procedure, theclinician must first designate the appropriate implant size. After thecervical fusion implant 110 is chosen, the engagement features 17 of theelongate fork member 11 are inserted into the apertures 12 on theimplant 110. At that time the cervical fusion implant 110 and elongatefork member 11 are slidably engaged with one another. Before theclinician can manipulate the combined cervical fusion implant 110 andelongated fork member 11, they must be releasably secured together. Inorder to secure the cervical fusion implant 110 onto the elongate forkmember 11, the clinician would next employ the tubular lock member 21.The clinician would insert the proximal end of the elongate fork member11 into the central bore 25 of the tubular lock member 21 at its distalend. The tubular lock member 21 would then be advanced over the elongatefork member 11 until the thread feature 13 of that member and the threadfeature 23 of the tubular lock member 21 become engaged.

Once engaged, advancement of the tubular lock member requires rotationof the tubular lock member 21 with respect to the elongate fork member11. Preferably, after only a small amount of engagement of the threadfeatures the distal end of the tubular lock member 21 would contact thetaper feature 19 of the elongate fork member 11. The tubular lock member21 would be advanced creating greater interference as the distal endapproaches the distal end of the taper feature 19 which has the largerouter dimension. The increasing interference would laterally displacethe clamping arms 15 of the elongate fork member 11 towards each other.Since the engagement features 17 of the elongate fork member 11 wereinitially inserted into the apertures 12 of the exemplary cervicalfusion implant 110, the displacement of the clamping arms 15 wouldcreate a compressive force on the purchase region 39 separating theapertures 12 of the exemplary cervical fusion implant 110. Thatcompressive force allows a clinician to manipulate the system withoutthe exemplary cervical fusion implant 110 becoming disengaged from thecervical inserter instrument 120.

The enhanced visualization features of the implants 10, 110 areexplained in greater detail with reference to FIGS. 18-23. FIG. 18illustrates an implant 10 dimensioned particularly for use in aposterior approach (PLIF) having (by way of example only) a widthranging between 9 and 11 mm, a height ranging between 8 and 14 mm, and alength ranging between 25 and 30 mm. FIG. 19 illustrates the implant 10of FIG. 18 from a side perspective via as taken via X-ray or fluoroscopytechniques, clearly showing the location of the spike elements 7 and 8(there is no central spike element 9 as with FIG. 1) relative to theimplant 10 and visualization apertures 4. FIG. 20 illustrates an implant10 dimensioned particularly for use in a lateral approach (XLIF™ byNuVasive) having (by way of example only) a width of approximately 18mm, a height ranging between 8 and 16 mm, and a length ranging between40 and 45 mm. FIG. 21 illustrates the implant 10 of FIG. 20 from a sideperspective via as taken via X-ray or fluoroscopy techniques, clearlyshowing the location of the spike elements 7, 8, 9 relative to theimplant 10 and visualization apertures 4. FIG. 22 illustrates an implant110 dimensioned particularly for use in the cervical spine having (byway of example only) a width of approximately 11 mm, a height rangingbetween 5 and 12 mm, and a length of approximately 14 mm. FIG. 23illustrates the implant 110 of FIG. 22 from a side perspective via astaken via X-ray or fluoroscopy techniques, clearly showing the locationof the spike elements 66 relative to the implant 110 and visualizationapertures 4. In this fashion, a surgeon may easily track the progress ofthe implant 10, 110 during implantation and/or after implantation byvisualizing the spike elements 7,8,9 and 66, respectively, under X-rayand/or fluoroscopy according to the present invention.

While the invention is susceptible to various modifications andalternative forms, specific embodiments thereof have been shown by wayof example in the drawings and are herein described in detail. It shouldbe understood, however, that the description herein of specificembodiments is not intended to limit the invention to the particularforms disclosed, but on the contrary, the invention is to cover allmodifications, equivalents, and alternatives falling within the spiritand scope of the invention as defined by the appended claims.

For example, while described herein primarily with reference to thelumbar and cervical spinal surgery, it is to be readily appreciated thatthe spinal fusion implants of the present invention may be suitable foraccomplishing fusion in the thoracic spine without departing from thescope of the present invention. Moreover, it is to be readilyappreciated that the insertion tools described herein may be employedwith implants of any number of suitable constructions, including but notlimited to metal, ceramic, plastic or composite.

What is claimed is:
 1. A spinal fusion implant of non-bone constructionpositionable within an interbody space between a first vertebra and asecond vertebra, said implant comprising: an upper surface includinggenerally parallel ridges to contact said first vertebra when saidimplant is positioned within the interbody space, a lower surfaceincluding generally parallel ridges to contact said second vertebra whensaid implant is positioned within the interbody space, a distal wall, aproximal wall, a first sidewall, and a second sidewall generallyopposite from the first sidewall, wherein said distal wall, proximalwall, first sidewall, and second sidewall comprise a radiolucentmaterial; wherein said implant has a longitudinal length extending froma proximal end of said proximal wall to a distal end of said distalwall, wherein said longitudinal length of said implant is greater than40 mm said implant has a maximum lateral width extending from said firstsidewall to said second sidewall along a medial plane that is generallyperpendicular to said longitudinal length, said implant has a heightextending from said upper surface to said lower surface and extendinggenerally perpendicular to said longitudinal length and said maximumlateral width, wherein said longitudinal length is greater than saidmaximum lateral width, and said maximum lateral width is greater thansaid height; a threaded receiving aperture configured to releasable matewith an inserter tool, the threaded receiving aperture extending intosaid proximal wall and having a central longitudinal axis generallyparallel to said longitudinal length of said implant; first and secondlateral grooves positioned in said proximal wall and positionedlaterally of said threaded receiving aperture; at least a first fusionaperture extending through said upper surface and lower surface andconfigured to permit bone growth between the first vertebra and thesecond vertebra when said implant is positioned within the interbodyspace, wherein the first fusion aperture is symmetric about the centrallongitudinal axis of the threaded receiving aperture, said first fusionaperture having: a longitudinal aperture length extending generallyparallel to the longitudinal length of said implant, and a lateralaperture width extending between said first sidewall to said secondsidewall, wherein the longitudinal aperture length is greater than thelateral aperture width; and first, second, third, and fourth radiopaquemarkers positioned in said radiolucent material, each of said first,second, third, and fourth radiopaque markers including an elongate bodyoriented generally parallel to said height of the implant, wherein thefirst radiopaque marker is positioned in said distal wall, wherein thesecond radiopaque marker is positioned in said proximal wall, whereinthe third radiopaque marker is positioned in the first sidewall andextends in the medial plane, wherein the fourth radiopaque marker ispositioned in the second sidewall and extends in the medial plane. 2.The spinal fusion implant of claim 1, wherein said generally parallelridges of said upper surface extend generally perpendicular to saidlongitudinal length.
 3. The spinal fusion implant of claim 2, whereintwo of said generally parallel ridges extend over a medial support wallextending between the first and second sidewalls, wherein said medialsupport wall is positioned along said medial plane.
 4. The spinal fusionimplant of claim 3, wherein said generally parallel ridges of said uppersurface are configured to be anti-migration elements to engage the firstvertebra when said implant is positioned within the interbody space. 5.The spinal fusion implant of claim 4, wherein said generally parallelridges of said lower surface extend generally perpendicular to saidlongitudinal length, and wherein said generally parallel ridges of saidlower surface are configured to be anti-migration elements to engage thesecond vertebra when said implant is positioned within the interbodyspace.
 6. The spinal fusion implant of claim 1, further comprising amedial support wall extending between the first and second sidewalls,wherein said medial support wall is positioned along said medial plane.7. The spinal fusion implant of claim 6, wherein the implant comprisesthe first fusion aperture and a second fusion aperture extending throughsaid upper surface and lower surface and configured to permit bonegrowth between the first vertebra and the second vertebra when saidimplant is positioned within the interbody space, wherein the first andsecond fusion apertures are positioned on opposite sides of the medialsupport wall.
 8. The spinal fusion implant of claim 7, wherein the firstfusion aperture is symmetric with the second fusion aperture relative tothe medial plane.
 9. The spinal fusion implant of claim 1, wherein saidheight of said implant extends in said medial plane, and wherein saidheight of said implant is greater than a distal face height of saiddistal wall and is greater than a proximal face height of said proximalwall.
 10. The spinal fusion implant of claim 9, wherein said proximalface height of said proximal wall is greater than said distal faceheight of said distal wall.
 11. The spinal fusion implant of claim 1,wherein said implant includes four openings defined in said secondsidewall, a first pair of said four openings being located in the secondsidewall on a first said of said medial plane, and a second pair of saidfour openings being located on a first said of said medial plane. 12.The spinal fusion implant of claim 11, wherein the four openings definedin said second sidewall have the same shape.
 13. The spinal fusionimplant of claim 1, wherein said first radiopaque marker is symmetricwith the second radiopaque marker relative to said medial plane.
 14. Thespinal fusion implant of claim 13, wherein said third radiopaque markeris symmetric with the fourth radiopaque marker relative to a centrallongitudinal plane extending along the central longitudinal axis of thethreaded receiving aperture and generally parallel to said height of theimplant.
 15. The spinal fusion implant of claim 1, wherein said firstsidewall is symmetric with said second sidewall relative to the centrallongitudinal axis of the threaded receiving aperture.
 16. The spinalfusion implant of claim 15, wherein said first and second sidewalls eachdefine at least one viewing aperture in communication with the firstfusion aperture, wherein said at least one viewing aperture of the firstsidewall is symmetric with said at least one viewing aperture of thesecond sidewall relative to the central longitudinal axis of thethreaded receiving aperture.
 17. The spinal fusion implant of claim 1,wherein the maximum longitudinal length of the implant is at least twoand half times greater than the maximum lateral width.
 18. The spinalfusion implant of claim 17, wherein said maximum lateral width of saidimplant is approximately 18 mm.
 19. The spinal fusion implant of claim1, wherein said first and second sidewalls each include an outwardlybowed surface portion facing outwardly away from said first fusionaperture, wherein a convex curvature of the outwardly bowed surfaceportion of the first sidewall is symmetric with a convex curvature ofthe outwardly bowed surface portion of the second sidewall relative to acentral longitudinal plane extending along the central longitudinal axisof the threaded receiving aperture and generally parallel to said heightof the implant.
 20. The spinal fusion implant of claim 19, wherein saidfirst and second sidewalls each define at least one viewing aperture incommunication with the first fusion aperture wherein said at least oneviewing aperture of the first sidewall is symmetric with said at leastone viewing aperture of the second sidewall relative to the centrallongitudinal plane.
 21. The spinal fusion implant of claim 1, whereinsaid maximum lateral width of said implant is approximately 18 mm. 22.The spinal fusion implant of claim 1, wherein said maximum lateral widthof said implant is greater than a maximum lateral width of said distalwall and is greater than a maximum lateral width of said proximal wall.23. The spinal fusion implant of claim 1, wherein said threadedreceiving aperture and said first and second lateral grooves areconfigured to releasably mate with a lateral, trans-psoas inserter tool.24. The spinal fusion implant of claim 1, wherein said radiolucentmaterial comprises PEEK.
 25. The spinal fusion implant of claim 1,wherein said implant includes at least one visualization apertureextending through at least one of said first sidewall and said secondsidewall.
 26. The spinal fusion implant of claim 1, wherein said upperand lower surfaces are generally parallel to one another.
 27. The spinalfusion implant of claim 1, wherein said upper and lower surfaces aregenerally angled relative to one another to approximately correspond tolordosis of a lumbar spine when said implant is positioned within theinterbody space.
 28. The spinal fusion implant of claim 1, wherein saidfirst fusion aperture is one of generally rectangular and generallyoblong in shape.
 29. The spinal fusion implant of claim 1, wherein thelateral aperture width of said first fusion aperture is more than twotime greater than a lateral thickness of said first sidewall and is morethan two time greater than a lateral thickness of said second sidewall.30. The spinal fusion implant of claim 1, further comprising anosteoinductive material positioned with said first fusion aperture. 31.The spinal fusion implant of claim 1, wherein said first and secondsidewalls each include an outwardly bowed surface portion facingoutwardly away from said first fusion aperture, wherein a convexcurvature of the outwardly bowed surface portion of the first sidewallis symmetric with a convex curvature of the outwardly bowed surfaceportion of the second sidewall relative to the central longitudinal axisof the threaded receiving aperture.
 32. The spinal fusion implant ofclaim 1, further comprising fifth and sixth radiopaque markerspositioned in said radiolucent material, wherein the fifth radiopaquemarker is positioned in said distal wall, wherein the sixth radiopaquemarker is positioned in said proximal wall.